On Thursday, August 13, 2020 at 5:32:17 AM UTC+2 syzbot wrote:

quoted

syzbot has found a reproducer for the following issue on:

HEAD commit: ce8056d1 wip: changed copy_from_user where instrumented
git tree: https://github.com/google/kmsan.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=12985a16900000
kernel config: https://syzkaller.appspot.com/x/.config?x=3afe005fb99591f
dashboard link: https://syzkaller.appspot.com/bug?extid=2ca247c2d60c7023de7f
compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1468efe2900000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10bb9fba900000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2ca247...@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in ath9k_htc_rx_msg+0x28f/0x1f50 drivers/net/wireless/ath/ath9k/htc_hst.c:410
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.8.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
<IRQ>
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x21c/0x280 lib/dump_stack.c:118
kmsan_report+0xf7/0x1e0 mm/kmsan/kmsan_report.c:121
__msan_warning+0x58/0xa0 mm/kmsan/kmsan_instr.c:215
ath9k_htc_rx_msg+0x28f/0x1f50 drivers/net/wireless/ath/ath9k/htc_hst.c:410
ath9k_hif_usb_rx_stream drivers/net/wireless/ath/ath9k/hif_usb.c:638 [inline]
ath9k_hif_usb_rx_cb+0x1841/0x1d10 drivers/net/wireless/ath/ath9k/hif_usb.c:671
__usb_hcd_giveback_urb+0x687/0x870 drivers/usb/core/hcd.c:1650
usb_hcd_giveback_urb+0x1cb/0x730 drivers/usb/core/hcd.c:1716
dummy_timer+0xd98/0x71c0 drivers/usb/gadget/udc/dummy_hcd.c:1967
call_timer_fn+0x226/0x550 kernel/time/timer.c:1404
expire_timers+0x4fc/0x780 kernel/time/timer.c:1449
__run_timers+0xaf4/0xd30 kernel/time/timer.c:1773
run_timer_softirq+0x2d/0x50 kernel/time/timer.c:1786
__do_softirq+0x2ea/0x7f5 kernel/softirq.c:293
asm_call_on_stack+0xf/0x20 arch/x86/entry/entry_64.S:711
</IRQ>
__run_on_irqstack arch/x86/include/asm/irq_stack.h:23 [inline]
run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:50 [inline]
do_softirq_own_stack+0x7c/0xa0 arch/x86/kernel/irq_64.c:77
invoke_softirq kernel/softirq.c:390 [inline]
__irq_exit_rcu+0x226/0x270 kernel/softirq.c:420
irq_exit_rcu+0xe/0x10 kernel/softirq.c:432
sysvec_apic_timer_interrupt+0x107/0x130 arch/x86/kernel/apic/apic.c:1091
asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:593
RIP: 0010:native_irq_disable arch/x86/include/asm/irqflags.h:49 [inline]
RIP: 0010:arch_local_irq_disable arch/x86/include/asm/irqflags.h:89 [inline]
RIP: 0010:acpi_safe_halt drivers/acpi/processor_idle.c:112 [inline]
RIP: 0010:acpi_idle_do_entry drivers/acpi/processor_idle.c:525 [inline]
RIP: 0010:acpi_idle_enter+0x817/0xeb0 drivers/acpi/processor_idle.c:651
Code: 85 db 74 0a f7 d3 44 21 fb 48 85 db 74 32 4d 85 ff 75 3a 48 8b 5d a0 e9 0c 00 00 00 e8 12 b2 78 fb 0f 00 2d 25 15 1c 0b fb f4 <fa> eb 5a 84 c0 8b 7d 90 0f 45 7d 94 e8 d8 9a f4 fb e9 74 fc ff ff
RSP: 0018:ffff88812df93bc8 EFLAGS: 00000246
RAX: 0000000000000000 RBX: ffff8881dfefce70 RCX: 000000012db88000
RDX: ffff88812df88000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffff88812df93ca0 R08: ffffffff86420acc R09: ffff88812fffa000
R10: 0000000000000002 R11: ffff88812df88000 R12: ffff88812df889d8
R13: ffff8881dfefcc64 R14: 0000000000000000 R15: 0000000000000000
cpuidle_enter_state+0x860/0x12b0 drivers/cpuidle/cpuidle.c:235
cpuidle_enter+0xe3/0x170 drivers/cpuidle/cpuidle.c:346
call_cpuidle kernel/sched/idle.c:126 [inline]
cpuidle_idle_call kernel/sched/idle.c:214 [inline]
do_idle+0x668/0x810 kernel/sched/idle.c:276
cpu_startup_entry+0x45/0x50 kernel/sched/idle.c:372
start_secondary+0x1bf/0x240 arch/x86/kernel/smpboot.c:268
secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243

Uninit was created at:
kmsan_save_stack_with_flags+0x3c/0x90 mm/kmsan/kmsan.c:144
kmsan_internal_alloc_meta_for_pages mm/kmsan/kmsan_shadow.c:269 [inline]
kmsan_alloc_page+0xc5/0x1a0 mm/kmsan/kmsan_shadow.c:293
__alloc_pages_nodemask+0xdf0/0x1030 mm/page_alloc.c:4889
__alloc_pages include/linux/gfp.h:509 [inline]
__alloc_pages_node include/linux/gfp.h:522 [inline]
alloc_pages_node include/linux/gfp.h:536 [inline]
__page_frag_cache_refill mm/page_alloc.c:4964 [inline]
page_frag_alloc+0x35b/0x880 mm/page_alloc.c:4994
__netdev_alloc_skb+0x2a8/0xc90 net/core/skbuff.c:451
__dev_alloc_skb include/linux/skbuff.h:2813 [inline]
ath9k_hif_usb_rx_stream drivers/net/wireless/ath/ath9k/hif_usb.c:620 [inline]
ath9k_hif_usb_rx_cb+0xe5a/0x1d10 drivers/net/wireless/ath/ath9k/hif_usb.c:671
__usb_hcd_giveback_urb+0x687/0x870 drivers/usb/core/hcd.c:1650
usb_hcd_giveback_urb+0x1cb/0x730 drivers/usb/core/hcd.c:1716
dummy_timer+0xd98/0x71c0 drivers/usb/gadget/udc/dummy_hcd.c:1967
call_timer_fn+0x226/0x550 kernel/time/timer.c:1404
expire_timers+0x4fc/0x780 kernel/time/timer.c:1449
__run_timers+0xaf4/0xd30 kernel/time/timer.c:1773
run_timer_softirq+0x2d/0x50 kernel/time/timer.c:1786
__do_softirq+0x2ea/0x7f5 kernel/softirq.c:293
=====================================================

This bug bites us quite often on syzbot: https://syzkaller.appspot.com/bug?id=659ddf411502a2fe220c8f9be696d5a8d8db726e (17k crashes)
The patch below by phil@philpotter.co.uk (https://syzkaller.appspot.com/text?tag=Patch&x=173dcb51d00000) seems to fix the problem, but I have no idea what's going on there.

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diff --git a/drivers/net/wireless/ath/ath9k/htc_hst.c b/drivers/net/wireless/ath/ath9k/htc_hst.c
index 510e61e97dbc..9dbfff7a388e 100644
--- a/drivers/net/wireless/ath/ath9k/htc_hst.c
+++ b/drivers/net/wireless/ath/ath9k/htc_hst.c

@@ -403,7 +403,7 @@ void ath9k_htc_rx_msg(struct htc_target *htc_handle,
     struct htc_endpoint *endpoint;
     __be16 *msg_id;

-    if (!htc_handle || !skb)
+    if (!htc_handle || !skb || !pskb_may_pull(skb, sizeof(struct htc_frame_hdr)))
         return;

     htc_hdr = (struct htc_frame_hdr *) skb->data;

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